(1) Field of the Invention
The present invention relates to a dust collection apparatus and more particularly to such a dust collection apparatus which sucks dust, odors or gas generated in a factory, and discharges same outside.
(2) Description of the Prior Art
Conventionally, in a factory where dust was generated, a number of discharge fans, which were mounted on the walls of a building of the factory, discharged the dust outside directly or via ducts.
However, in a case of a welding factory, welding locations generating dust, ordors or gas were ordinary dispersed therein.
Therefore, it could not obtain an effective dust proof for welders who were working at places between the welding locations generating dust and gas and the walls of the factory where the discharge fans were positioned. To solve such a problem, it was proposed such a dust collection system that a collection duct was installed independently at the dust and gas generating locations so as to suck the generated dust and gas immediately and discharge same outside via a main suction pump. The collection duct had to include such a construction that it could approach the welding place and be remote away therefrom according to welding conditions. For the purpose, it was proposed that the collection duct was constructed by utilizing a flexible hose of plastices. In this case, the hose was mounted on a support arm which was fixed on a carrier (for instance, U.S. Pat. No. 3,150,404) or a floor of the factory and extended upward.
In the welding factory, however, since the plastice hose sucked sparks and fumes or griding powder, it was easily damaged and could not be used for a long time. Further, when such a dust collection system was large sized for increasing a collection capacity, the support arm could not support a heavy hose and the support arm itself had to be large sized. As the result, there occurred a problem that the collection system per se became larger and larger.
The inventor proposed a duct collection apparatus in Japanese Utility Model Application No. 63-130807, wherein a plurality of metal ducts were disposed to be bendable by utilizing a mechanism like a magic-hand without using a support arm and a plastic hose. This dust collection apparatus comprised as follows. A suction duct connected to a suction pump was connected to a base duct which was fixed on a floor to stand thereon. A rotatable duct was connected rotatably to the base duct and driven by means of a hydraulic cylinder. A first duct arm was pivoted on the upper portion of the rotatable duct so as to be swingable up and down about a horizontal axis. The first duct arm was driven to swing by means of a hydraulic cylinder which was attached to the rotatable duct with one end thereof and to the first duct arm with another end thereof. The forward end of the first duct arm may be bent at a predetermined angle and a second duct arm was pivoted on the forward end of the first duct arm to be able to swing up and down about a horizontal axis. The second duct arm was swung by means of a hydraulic cylinder which was mounted on the first duct arm with one end thereof and the second duct arm with another end thereof. The duct could be close to and remote away from the welding locations within a range covered by operations of the rotatable duct and the first and second duct arms. A hood arm was connected to a forward end of the second duct arm to extend in a direction vertical to a longitudinal direction of the second duct arm and it is constructed to keep its desired rotated positions.
The dust collection apparatus solved a problem raised in a conventional dust collection apparatus which used a support arm and a plastic hose. However, there should be provided respectively a rotatable connection between the rotatable duct, the first and second duct arms, the second duct arm and the hood arm, forming a suction passage therethrough. Further, the second duct arm had to support a weight of the hood arm and the first duct arm had to support weights of the second duct arm and the hood arm. Also, the rotatable duct had to support all of the weights of the first and second duct arms and the hood arm. Of course, an effective discharge could be secured by decreasing an air resistance in the duct. However, the connecting portions between these arms connect the walls of the arms which were faced and rotatably contacted to one another. Therefore, the duct could be deformed due to a weight load acting on the connecting portions and as the result a smooth rotation could not be obtained for these arms unless the duct was made by a heavy and strong steel plate.
Further, such an arm deformation caused a decrease of a suction effect since clearances were formed and widened around the pivots for connecting the arms to one another. For solving the problem, it could provide ribs for reinforcing the connecting portions. However, this construction lowered a suction effect since the ribs increased an air resistance in the duct.